Of course everything helps. Probably none is *required* though, at least to start. When you find something that you can't figure out, look at the context to figure out what it's probably doing, and then google that. See if it lines up.
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A word of warning:
Signal processing functions often involve weird math. It's all simple operations, like multiplication and addition, but when you look at the equations, or the code that implements those equations, it's not at all intuitive that "that's an EQ", or whatever, aside from the function names and comments.
Those that do understand it intuitively, live in a (very!) abstract world. These things *are* intuitive over there, once you understand the rules, but the rules are nothing like what we're used to physically, even though there is a 1:1 mathematical translation from one to the other and back again. (that translation is not at all intuitive either, for most people)
System management - passing data around, not clobbering things, and keeping all of that straight - as difficult as it is, is nothing compared to the weirdness in signal processing.
Encoding...uses signal processing in a weird way, so that *really* gets wacky! I sometimes describe it as an optimizing compiler, where the encoded bitstream is the machine code...
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If you really want to dive into it, go right ahead! Maybe you'll find something useful that everyone else missed. But it's not for the feint of heart!
